The present invention relates to devices for injecting, infusing, administering, delivering or dispensing a substance, and to methods of making and using such devices. More particularly, it relates to a conveying device in or for an apparatus for administering a product. In some embodiments, the apparatus can be an infusion apparatus or injection apparatus for administering a drug, a diagnostic agent or in principle any other product which can be administered to a human or animal subject. One preferred application or use of the device and method of the present invention is for the self-administering of drugs, in particular administering insulin in the treatment of diabetes.
In many cases, infusion apparatus and injection apparatus for administering the product in exact doses employ a threaded drive to convert a torque of a drive motor into an axial translational movement of a conveying member in the threaded engagement and to deliver the product from a reservoir of the infusion apparatus or injection apparatus by the axial movement. Once the reservoir has been emptied, the conveying member has to be rotated back in the threaded engagement into an initial position to be used again, which can either be laboriously performed manually or requires a direction-reversible drive motor which consumes energy for the reverse rotation.
WO 2005/094921 A1 proposes a threaded drive comprising two conveying members in a threaded engagement, one of which is slit in the region of its thread and is therefore radially flexible. The relevant conveying member can therefore be axially pushed into threaded engagement with the other conveying member, up to and against a stopper, without a rotational movement. to be able to establish the threaded engagement in the stopper position despite the radial flexibility, however, the conveying member which is flexible in the region of its thread has to be rotated about the threaded axis in the stopper position. Establishing the threaded engagement requires a particular hand operation and therefore particular concentration and dexterity at the end of axial insertion. This is in particular problematic for applications in which the user administers the product himself, for example in the treatment of diabetes. WO 2005/094921 A1 also describes a modified mechanism in which the threaded engagement is automatically established when the conveying member is pushed in. In the modification, a flexible thread region is created by segments which project radially with respect to the threaded axis, can be elastically bent and are therefore correspondingly slender, and which together form the thread of the conveying member. When the conveying member is pushed in, the bendable segments slide elastically over the thread of the other conveying member. In the threaded engagement, the segments forming the flexible thread therefore always press, with their spring force which is based on bending elasticity, into the turns of the thread of the other conveying member. A corresponding amount of energy is needed for the drive.